1. Field of the Invention
The present invention relates to friction clutches including a flexible torque transmitting flywheel, especially for motor vehicles.
2. Description of Related Art
Related art flywheels include a flexible disc carrying a plate which is part of a friction clutch.
In that document the clutch with its flywheel is interposed in the transmission train going from the internal combustion engine to the unit that transmits motion to the wheels of the vehicle.
The disc comprises, firstly at its inner periphery, a first portion for coupling the friction clutch in rotation with the output shaft of the internal combustion engine of the vehicle, which in this case is the crankshaft of the engine, and secondly at its outer periphery, a second portion for supporting a plate which in one embodiment is the reaction plate.
Flexibility of the disc is such that, having regard to the inertia of the clutch, the natural frequency of the assembly lies in the range between fifty and two hundred hertz, and more precisely close to ninety hertz for a touring vehicle.
This natural frequency, referred to as a first frequency, is a bending frequency of the flywheel, with the disc then carrying out a nutation movement about its diameter.
Tests have shown the existence, above two hundred hertz, of a second natural frequency referred to as a pumping frequency, which is higher than the first frequency or so-called bending frequency.
It can result from this that the frequencies are coupled, with poor vibration absorption and the occurrence of noise.
An object of the present invention is to overcome these drawbacks in a simple and inexpensive way.